Someone coincidentally asked the same question in another forum. I'll post my
response here as well.
More or less here's what'll happen:
1. Someone submits an invalid WHOIS report via the registrar or the report link.
2. The registrar eventually receives the report. (of course!)
3. They'll try to notify the domain's registrant and contacts at least via email.
Via postal mail, phone, and fax depends on the registrar being able to afford
doing them.
4. If the registrant and/or its contacts (admin & tech)
do get the notice, they
will be forced make any needed corrections (if any) and notify the registrar of
such. The registrar might ask for extra requirements which they've no choice
but to comply.
5. If the registrant and/or its contacts don't get the notice and don't respond
after some time (at least 5 days, I think), the registrar will disable any
website, email, or whatever access to the domain name. This should get the
contacts' attention.
6. If the registrant and/or its contacts finally ask the registrar what happened
to the domain, the registrar will explain the invalid WHOIS report and "force"
the contacts to follow their instructions and submit any documents, if any.
The registrar can even "fine" the domain's contacts for it if they opt to.
7. The registrant and/or contacts have no choice but to comply. If they still
don't respond or even refuse to "obey" the registrar, the registrar can choose
to delete the name eventually.
8. Once the name's deleted, it'll fall into redemption period, pending delete,
etc.
Incidentally I wrote of one such extreme case in my
blog.
Anyway, more or less what I posted above is what will happen. The registrar
can ask (or some people would think demand) for extra things, and they
decide on the timeframe.